1. Field of the Invention
The invention relates to a rolling bearing and, more particularly, to a rolling bearing that is suitable when used in a drive roll or driven roll of a continuous casting machine.
2. Description of the Related Art
In an existing art, a rolling bearing includes a cylindrical roller bearing that is described in Japanese Utility Model Application Publication No. 63-142419 (JP-U-63-142419) (FIG. 3). A rolling bearing unit includes a shaft member, a housing member, a loose rib and a snap ring, and the cylindrical roller bearing is arranged on the shaft member. The cylindrical roller bearing includes an aligning ring, an outer ring, an inner ring and a plurality of cylindrical rollers. The aligning ring has an inner surface formed of part of a spherical surface. The outer ring has an outer surface formed of part of a spherical surface.
The aligning ring is fixed onto an inner peripheral surface of the housing member. The outer surface of the outer ring is fitted to the inner surface of the aligning ring. The outer ring has ribs respectively on one side and the other side of a raceway surface.
On the other hand, the inner ring is fixedly fitted around an outer peripheral surface of the shaft member. One end surface of the inner ring in the axial direction is in contact with a step of the shaft member.
The inner ring has a rib on one side of a raceway surface in the axial direction. The snap ring is fitted in an annular groove of the shaft member. In addition, the loose rib is fixedly fitted around the shaft member. The loose rib is axially held by the other end surface of the inner ring in the axial direction and the snap ring. In addition, the plurality of cylindrical rollers are arranged between the raceway surface of the outer ring and the raceway surface of the inner ring so that they do not overlap one another in the axial direction.
When an axial load acts on the rolling bearing unit, the rolling bearing unit transmits force in order of the step of the shaft member, the rib at one side of the inner ring, the cylindrical rollers, the rib of the outer ring at the other side in the axial direction, the aligning ring and the housing member to receive the axial load, or adds force in order of the snap ring, the loose rib, the cylindrical rollers, the rib of the outer ring at one side in the axial direction, the aligning ring and the housing member to receive the axial load.
In the rolling bearing unit, an axial load is withstood by sliding contact between the end surfaces of the rolling cylindrical rollers and the rib or loose rib. Thus, particularly, under the specifications of extremely low rotational speeds as in the case used in a continuous casting machine, it is difficult to form an oil film. Then, as a result, in the cylindrical roller bearing, metal contact occurs between the end surfaces of the cylindrical rollers and the rib. This may produce galling on the end surfaces of the cylindrical rollers or the rib.
In addition, particularly, in the case where the cylindrical roller bearing is a full complement roller bearing that has no retainer, when the roller bearing receives an axial load and then rollers are about to fall down, the rib contacts with the end surfaces of the rollers at their edges to thereby locally increase contact pressure. This may produce galling on the end surfaces of the cylindrical rollers or the rib.